There are many industrially important operations in which it is necessary to introduce a quench stream, a catalyst stream or some other secondary stream into a primary stream which is being passed through a contacting device or reactor. Typical of some of these commercially important operations are hydrofining of oils, hydrocracking of heavy hydrocarbons into lighter compounds, synthesis of ammonia and oxonation of olefins to aldehydes. In such operations, it is very often necessary to add the secondary streams to obtain certain benefits, e.g., introducing a quench stream to remove reaction heat and thereby control reactor temperature, adding catalyst to replace that which has already been consumed and thereby controlling the progress of a chemical reaction, adding a reactant to replace that which has been consumed, or providing an excess needed to obtain the maximum yield from a chemical reaction.
In reactions where the primary stream is a mixture of liquid and gas, as exemplified by hydrofining, hydrocracking and oxonation reactions, it is particularly difficult to assure good mixing of the secondary streams with the primary stream. This is due to the fact that gases and liquid tend to separate unless they are traveling at such speeds that they are inherently mixed. However, in commercial reactors where a relatively long residence time is required, the fow rates are such that the separation of gas and liquid is quite significant especially in upfow reactors. In such instances the chemical reaction is not as uniform as it would be with good mixing of gas and liquid. The introduction of quench or other secondary streams becomes much more difficult and the design of mixing facilities becomes critical to the overall performance of the reactor itself.
The prior art shows a number of ways in which such secondary streams may be introduced. They may include any or a combination of the following typical mixing devices. Slotted plates may be used to obtain mixing by entrainment on the downstream side of the slots and by sparging the secondary stream into the jet created by the slots in the plates. A similar operation may be performed using perforated trays, bubble type cap trays or such similar devices as are used in fractionating towers. Beds packed with Raschig rings, Berl saddles or other commercially available packing materials may be used in order to break up the large bubbles of gas which may tend to be formed in the liquid and also to improve the contacting of the gas and liquid with the secondary streams. Special spargers may be used to distribute the secondary stream uniformly across the reactor. Any number of devices have been suggested in the prior art, substantially all of which have proven quite unsatisfactory.
The present invention presents a novel combination of mechanical elements which make possible extremely good mixing of the three phases, i.e., the liquid and gas of the primary stream and the secondary stream. This invention is especially useful where performance of prior art devices indicates that temperature or reaction control are less than satisfactory and optimum performance of the reaction system has not been achieved. The present invention provides exceptionally effective mixing and makes possible the control of reactions which have heretofore been marginally operable when using prior art devices.